Unexplained high frequency (24-30%) of acute pro-myelocytic leukemia (APL) has been reported among Hispanic populations. The aim of this joint project between the University of Texas MD Anderson Cancer Center (MDACC), the Instituto de Enfermedades Neplasicas (IEN) in Lima Peru, and the Puerto Rico Cancer Center (PRCC), University of Puerto Rico is to obtain preliminary epidemiologic cytogenetic, and molecular parameters that would allow to establish the feasibility of larger comparative multi-country study. For this purpose, the newly diagnosed APL patients admitted to the three centers will be asked to participate in an epidemiologic survey and will be examined for each of the 4 genes (PLM, PLZF, NPM and NuMA) that could fuse to retinoic acid receptor-alpha (RARalpha) and the retinoic acid specific catabolic enzyme CYP26. We will look for the similarities and differences among the partner proteins in these patients that may explain the high incidence and/or distinct clinical outcome in response to retinoic acid (RA) therapy.